The present invention relates to an information communication network.
Along with development in the information-oriented society, various information communication networks are available. One type of such information communication networks is a bidirectional CATV in which coaxial cable television as a broadcast network is bidirectionally combined with the information communication network, or broadband network. In the CATV, coaxial cables are extended along roads, and various types of video information are supplied to subscribers. The CATV network normally is a broadband network.
The broadband network is a bidirectional transmission path. However, since a signal is frequency-division multiplexed, it flows in one direction. More specifically, an upstream signal sent from a terminal device is returned at a head end, and is transmitted as a downstream signal. Since a signal is returned at the head end, this network is also called a U-shaped bus.
In the conventional CATV network, when some abnormality of a transmission path, e.g., cable disconnection or cable abnormality occurs, information can no longer flow through a transmission path downstream of the abnormal position. In the conventional CATV network, if malicious signal disturbance occurs, it affects the entire system.
Another prior art is a packet network based on the protocol of "Omninet" (Trademark notice of Corvus Corp.) wherein some nodes are constituted in a matrix. In this network, packets are sent from a transmission node to a reception node via a shortest path. If some trouble occurs on a transmission path, another shortest path is selected. A packet routine algorithm in the packet network is based on the "first come first served" means.